Separation of coarse light minerals in multiple cyclone-separator stages



Feb. 9, 1954 K. A. FERN ET AL SEPARATION OF COARSE LIGHT MINERALS IN MULTIPLE CYCLONE-SEPARATOR STAGES 2 Sheets-Sheet l Filed May 8, 1950 En CRU A. f4. FFP/V, Y

ATTORNEY K. A. FERN ET AL SEPARATION OF COARSE LIGHT MINERALS IN MULTIPLE CYCLONE`SEPARATOR STAGES 2 Sheets-Sheet 2 ATTORNEY Feb. 9, 1954 Filed May 8, 1950 .NNN

Patented Feb. 9, 1954 2,668,667

zstassv semaine orf coexistir rgIGiT amuse mf cron-ONE-SEP--n` ARAToResTAGEs:

@meer 'ber aliidlpy' 'efgarclone separator. The vortex nder dischag ,L- 'W containingwcoarse and v.ne light -materiaL-normally. gangue;and fine hea-vyemedium` particles, is introduced into`afsecond l1cyclone" separator.' Relativelydiiut'e vrtxlnderfd-ischarge from this ,msecond' cyclone `-septrato'r contfetinsA theV lightY `ere/sedi:3" grayity'niateial 'and seme ef the mie xileliumNv ndi; solids i' ,and'the'aexjdisolarge; which consists 'of soewliat'thicliendMediumsolids; isrecirculated cireuittgrinding:l y is'onlyfsuicien f E l Hel" A y gang'ue'gatlesefairerobtainedwiin `ltot) co'arse'fapar through theft cyclone: hmateral fron the' ticleifsizeefr effectiilef'tre-tmnt Onth'e other" .voltex discharge in the case of gold ores is ready handy-@fernegrindingeis downto:thef-sizeatfwhiene for jcyamdatien, and in pire ease-'ef' multiplethe-1 heavier? mineral constituents-farefliberated'l mineral ores, Suh aS DyritiC Coppel OIeS, iS Subfromlleaehlother; yor are-madesuitablelfoi'itratef jeted to suitable 'differential "treatment, foieil" mentpthe-fpow'erconsumption'forgrindingf'bew ample by flotation, if-desired; after classiaticin`"ir comes excessive andmcostsrisee` Inv casesl'whre f sto -remove -carse -ganguetheegangueftendstofformslime;eexeessivefslimefw The apexedischarge'fof thefrs't oylonewhi'chl formation-*also results; -.Whic1f1-introducesearradei conta-ins' coarsefheavymaterialandfinemedium* ditonalsevere-pr0b1em==- y so1ids,isground inw-a secondary:milleofFordinaryf' Aecordingeto the-present invention, the problemfdesignee-ande thene may-f4 be eitherY recirculatedf issolvedmy thee-use eofetwo stages of cycloneV sep-v throughethe -rst Acyclone for-mayf be mixed with# aration-with-fautogenousa medium in y series-Y toh the-,vortex =nder dischargew off? the {mfrstwcyclonee getherfA witld--aA` seondar-ytA grinding! circuitfA 'Iheand-passed-through-thesecondcyclone;I eitherf cyclone@ separation -is Yeiected' conventional/f cyclones"whielvoperaftewith-Isulicient fine hea-Vy materiaktejyaeb'asaemediumein cyclonefseparaticle-andthe apparatus usejdthereirr is described; -50 in anarticlebyeDrissen-P'Ihe Use of Centrifugali Fdrce forVL Cleaning1i neCoalin; I-lea-vy Liquidsandf"Sspe nsionsvx/ithA4 Special @eter-erica tothey I Cyclnelwshr"(The'urnal-'oTheflnstitutej stheaprocess;i ',Iv'heliirsirfflowsheetiillustratesthe1kg of *FelfDcex'nbr1945L and fornisthe subject'55 modicatioh n'which the apex discharge from being gradually reduced in size by the secondary mill until it iinally leay'esz'th'e' system with the vortex'ffnder 'dischargeV ofthe"lsecondecyclone The invent-ionWil-l be illustrated-byithe draw# ingsp inw-hiclrrgy case the coarser heavy material is recirculated,Nu

Fi'gsfel and-Zeareediagrammatic owsheets'fiofw `by the process of Fig. 2.

first cyclone contains siliceous gangue ground to f, A fr A the first cyclone, after being ground in the secondary mill, is mixed with the apex discharge of the second cyclone and recirculated through the first cyclone. Fig. 2 shows the alternative procedure, in which the ground apex discharge of the rst cyclone is passed through the second cyclone.

It will be noted that a very marked reduction in grinding costs is obtained. The preliminary closed circuit grinding is carried only to the point Where liberation of the heavy minerals fromlight gangue takes place. All of the light material is separated from the coarser heavy material in the first cyclone, and only the relatively smaller amount of the latter is ground to the small particle size necessary for liberation of the desired heavy mineral values. Only a small portion of the total ore is subjected to this ne grinding, with very great power savings.

The process has two other important advantages. First, the light material, such as gangue, is not ground to a fine size, with a resultant avoidance of excessive slime formation where slimy silicates are present. Secondly, the vortex nder discharge of the second cyclone contains only the nest of the heavy material.

The invention will be illustrated by typical examples of precious and base metal ores.

Example 1 A gold ore containing 1 oz. of gold per ton, mostly in the form of auriferous pyrite, assays approximatelyv sulfides and 90% siliceous gangue. This ore is treated by the process shown in Fig. 1, the overow to the first cyclone containing siliceous gangue ground to -35 mesh.

The vortex finder discharge from the second cyclone contains suldes of a neness of -325 mesh. This product is cyanided and produces a tailing residue having approximately the following composition:

Cyanidation Residue Oz. Au/ton siliceous Gangue 0.015 Sulde Ganmld.. 0.15 Total Residue 0. 028

As the suldes constitute only 10% of the ore, the power required for grinding them to -325 mesh is a very small part of the total power.

A comparison test, using standard procedure,

gives the following result: gangue ground to -65 mesh, suldes to a nominal 150 mesh. Cyanidation gives the following result:

' Cyanidation Residue Oz. Au/tou Siliceous Gangue 0.010 Sulde Gangue 0.30 Total Residue 0. 039

Example 2 A copper ore containing sulfides of copper associated with pyrite and siliceous gangue, and containing approximately 1.5% copper, is treated The overiiow to the -48 mesh. The vortex finder discharge of the second cyclone contains the siliceous gangue together with sulfides of a neness of approximately -325 mesh. This product is subjected to froth flotation Iusing dicresyl dithiophos'phoric acid as a promoter. A froth concentrate is obtained assaying approximately 25% copper, and

' a tailing assaying about 0.25% copper. The high conditions set forth above, a froth concentrate is tailing of approximately 0.25% copper.

obtained assaying just under 15% copper with a It will be noted that by the process of the present invention a much higher grade concentrate is obtained with no increase in grinding costs. In fact, the power required is slightly less because of the relatively much larger amount of siliceous gangue as compared to the suldes.

The iiowsheets, which illustrate the operation of the process with autogenous medium, represent the preferred modification as the heavy minerals have to be ground in any event and their use as medium solids entails no additional expense. It is possible, of course, to introduce into either or both of the cyclones exogenous mediuml solids, such as nely divided ferrosilicon or similar magnetic material.

However, When exogenous media are used, medium cleaning devices must be introduced with additional equipment cost; thereiore, while operative with exogenous media, the use of autogenous media is economically so much better that it constitutes the most practical embodiment of v.

the invention. Y Y

We claim:

1. A method of preparing ore for recovery processes, the ore containing light minerals and the plurality of heavy minerals, the light minerals having a very much greater average particle size than the heavy mineralsY which comprises grinding the ore to approximately the relatively coarse particle size at which it is desired to reject the light minerals, subjecting an aqueous suspension of the ground ore to cyclonic separation in the presence of nely divided heavy medium solids in suflicient concentration to produce a separating gravity in the cyclone greater than the specific gravity of the ne minerals whereby a vortex finder discharge is produced containing the light minerals, both coarse and line, associated with ne heavy mineral medium particles, and there is produced also an apex discharge containing heavy mineral only, subjecting the vortex finder discharge to a second cyclonic separation process at a gravity suiciently high so that the light minerals are discharged through a vortex nder associated with very ne heavy mineral particles and there is" produced an apex discharge containing onlyheavy mineral particles but of a particle size substantially coarser than the heavy mineral particles in the vortex iindr` discharge, grinding the apex discharge of the first cyclonic separation process and circulating I at least a portion of said ground discharge f' through the second cyclonic separation process,

recirculating the apex discharge from the's'econd'Y cyclonic separation process through the first as" the nely: divided medium solids and removing the vortex nder discharge from the second cyclonic separation in a form suitable for subjecting it to a separatory process capable of separating the very ne heavy mineral particles from the light particles.

2. A process according to claim 1 in which the ground apex discharge from the irst cyclonic separation process is recirculated directly therethrough a portion of said ground material thereby being discharged through the vortex nder discharge of the rst cyclonic separation process, and hence, subjected to the second cyclonic separation process.

3. A process according to claim 1 in which the ground apex discharge from the rst cyclonic separation process is mixed with the vortex finder discharge of the same process and the mixture subjected to the second cyclonic separation process.

4. A process according to claim 1 in which the ore is a gold ore, the gold being associated with a heavy mineral fraction liberatable from light mineral gangue at a size approximating that at which the first cyclonic separation process is effected.

5. A process according to claim 4 in Which the ground apex discharge from the first cyclonic separation process is recirculated directly therethrough a portion of said ground material thereby being discharged through the vortex nder discharge of the rst cyclonic separation process, and hence subjected to the second cyclonic separation process.

6. A process according to claim 4 in which the ground apex discharge from the rst cyclonic separation process is mixed with the vortex finder discharge of the same process and the mixture subjected to the second cyclonic separation process.

7. A process according to claim 1 in which the ore is a copper ore containing a plurality of copper minerals and the siliceous gangue separatable from the copper-containing minerals at a particle size approximating that at which the rst cyclonic separation process is carried out.

8. A process according to claim 7 in which the ground apex discharge from the first cyclonic separation process is recirculated directly therethrough a portion of said ground material thereby being discharged through the vortex nder discharge of the rst cyclonic separation process, and hence, subjected to the second cyclonic separation process.

9. A process according to claim 7 in which the ground apex discharge from the rst cyclonic separation process is mixed with the vortex nder discharge .of the same process and the mixture subjected to the second cyclonic separation process.

10. A process according to claim 1 in which the liberation of the light minerals is effected by closed circuit grinding in series with a sizing device and the undersize of the sizing device is subjected to the rst cyclonic separation process.

11. A process according to claim 1 in which the ore is a gold ore containing auriferous pyrite liberatable from light mineral gangue at approximately the particle size at which the rst cyclonic separation is effected.

12. A process according to claim 11 in which the ground apex discharge from the rst cyclonic separation process is recirculated directly therethrough a portion of said ground material thereby being discharged through the vortex nder discharge of the rst cyclonic separation process, and hence, subjected to the second cyclonic separation process.

13. A process according to claim 11 in which the ground apex discharge from the rst cyclonic separation process is mixed with the vortex finder discharge of the same process and the mixture subjected to the second cyclonic separation process.

KENNETH A. FERN. CHARLES F. ALLEN.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,526,519 Vogel-Jorgensen Oct. 17, 1950 OTHER REFERENCES The Use of Centrifugal Force etc. by Driessen, The Journal of The Institute of Fuel, December 1945. 

